Mouse tracking working intermittently after full screen

My application has some widgets that use setMouseTracking(true) so that they can receive move events and react to mouse hover.

This works fine in practice. However, my application has a feature where you can open a new detached widget and showFullScreen(). After closing the full screen widget, focus returns to my main window but mouse tracking is no longer working.

I can interact with widgets as if the window has normal focus. I implemented a quick check and confirmed that widgets that are supposed to have tracking still hasMouseTracking() == true

After a lot of clicking around, the widgets in question eventual return to active mouse tracking.

Is there some aspect of focus that Mac handles differently ? - On Linux I don't have this problem at all.